Mitochondrial GrpE is present in a complex with hsp70 and preproteins in transit across membranes.
We characterized a 24-kDa protein associated with matrix hsp70 (mt-hsp70) of Neurospora crassa and Saccharomyces cerevisiae mitochondria. By using specific antibodies, the protein was identified as MGE, a mitochondrial homolog of the prokaryotic heat shock protein GrpE. MGE extracted from mitochondria was quantitatively bound to hsp70. It was efficiently released ... from hsp70 by the addition of Mg-ATP but not by nonhydrolyzable ATP analogs or high salt. A mutant mt-hsp70, which was impaired in release of bound precursor proteins, released MGE in an ATP-dependent manner, indicating that precursor proteins and MGE bind to different sites of hsp70. A preprotein accumulated in transit across the mitochondrial membranes was specifically coprecipitated by either antibodies directed against MGE or antibodies directed against mt-hsp70. The preprotein accumulated at the outer membrane was not coprecipitated by either antibody preparation. After being imported into the matrix, the preprotein could be coprecipitated only by antibodies against mt-hsp70. We propose that mt-hsp70 and MGE cooperate in membrane translocation of preproteins.
Mesh Terms:
Ascomycota, Biological Transport, Cell Compartmentation, Fungal Proteins, Heat-Shock Proteins, Intracellular Membranes, Membrane Transport Proteins, Mitochondria, Mitochondrial Membrane Transport Proteins, Molecular Chaperones, Neurospora crassa, Protein Binding, Protein Precursors, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins
Ascomycota, Biological Transport, Cell Compartmentation, Fungal Proteins, Heat-Shock Proteins, Intracellular Membranes, Membrane Transport Proteins, Mitochondria, Mitochondrial Membrane Transport Proteins, Molecular Chaperones, Neurospora crassa, Protein Binding, Protein Precursors, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins
Mol. Cell. Biol.
Date: Oct. 01, 1994
PubMed ID: 7935381
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